> ## Documentation Index > Fetch the complete documentation index at: https://docs.corepillar.ai/llms.txt > Use this file to discover all available pages before exploring further. # Send a chat message > One ModelHub chat turn. The message (and any attachment text) is screened for personal data and masked before any model sees it, routed to a model (or the one you picked), and streamed back as server-sent events with masked values restored for you. Events, each as `data: {json}`: - `masked`: your turn in masked form, plus a display-safe reveal map - `routing`: which model was chosen and why, and the prompt tidy-up applied - `pii`: what the privacy scan found - `delta`: a chunk of the answer - `done`: final analysis, ids, masked history entries and the restore map - `error`: what went wrong A message containing a credential or government identifier is held: you get `pii` then `error`, and must resend with `overridePiiBlock: true`. The server keeps no conversation state; send prior turns in `history` (masked forms, from `done.masked`) and the accumulated `restoreMap`. **Auth:** session. **Permission:** member of the organization and project named in the body. ## OpenAPI ````yaml /api-reference/openapi.json post /chat/stream openapi: 3.1.0 info: title: CorePillar API version: 1.0.0 description: >- REST API for AgentHub and ModelHub. Ingestion endpoints authenticate with a project tracing key; all other endpoints use the signed-in user's browser session. servers: - url: https://pillarforge.corepillar.ai/api/v1 description: AgentHub security: [] tags: - name: Ingestion description: 'Send traces with a tracing key: JSON ingest and OpenTelemetry (OTLP).' - name: Traces description: Read traces and spans. - name: Evaluations description: Evaluate traces with evaluator collections. - name: Evaluators description: Built-in and custom evaluators. - name: Evaluator collections description: Ordered groups of evaluators. - name: Organizations description: Organizations you belong to. - name: Members description: Organization members, invites and roles. - name: Projects description: Projects inside an organization. - name: SSO description: Okta SSO configuration. - name: Tracing keys description: Create, list and revoke project tracing keys. - name: Cost calculator description: Estimate, generate and execute scenario runs. - name: Synthetic description: Synthetic agent and data setup from source material. - name: Chat description: ModelHub chat. Served at https://modelhub.corepillar.ai/api/v1. - name: Auth description: Sign-in helpers. - name: E2E description: Internal end-to-end encryption key directory. paths: /chat/stream: servers: - url: https://modelhub.corepillar.ai/api/v1 description: ModelHub post: tags: - Chat summary: Send a chat message description: >- One ModelHub chat turn. The message (and any attachment text) is screened for personal data and masked before any model sees it, routed to a model (or the one you picked), and streamed back as server-sent events with masked values restored for you. Events, each as `data: {json}`: - `masked`: your turn in masked form, plus a display-safe reveal map - `routing`: which model was chosen and why, and the prompt tidy-up applied - `pii`: what the privacy scan found - `delta`: a chunk of the answer - `done`: final analysis, ids, masked history entries and the restore map - `error`: what went wrong A message containing a credential or government identifier is held: you get `pii` then `error`, and must resend with `overridePiiBlock: true`. The server keeps no conversation state; send prior turns in `history` (masked forms, from `done.masked`) and the accumulated `restoreMap`. **Auth:** session. **Permission:** member of the organization and project named in the body. operationId: chatStream requestBody: required: true content: application/json: schema: type: object required: - conversationId - message - modelConfigId - orgSlug - projectSlug properties: conversationId: type: - string - 'null' format: uuid description: '`null` starts a new conversation.' history: type: array maxItems: 40 default: [] description: >- Prior turns, oldest first, in masked form. At most 20 exchanges. items: type: object required: - role - text properties: role: type: string enum: - user - assistant text: type: string message: type: string minLength: 1 maxLength: 32000 attachments: type: array maxItems: 5 default: [] description: >- Text from `POST /chat/attachments`. Up to 50,000 characters each and 100,000 in total. items: type: object required: - name - text properties: name: type: string minLength: 1 maxLength: 240 text: type: string minLength: 1 maxLength: 50000 modelConfigId: type: - string - 'null' format: uuid description: A specific model, or `null` to let routing choose. optimizePrompt: type: boolean default: true description: >- Tidy the prompt (whitespace, stock politeness) before sending. overridePiiBlock: type: boolean description: Continue after a held turn. The value is still masked. orgSlug: type: string minLength: 1 projectSlug: type: string minLength: 1 restoreMap: type: object additionalProperties: type: string maxLength: 2000 description: >- Placeholder to real value, accumulated from earlier `done` events. At most 400 entries. responses: '200': description: Server-sent event stream. content: text/event-stream: schema: type: string example: >+ data: {"type":"masked","user":"Email [EMAIL_01] the summary","revealMap":{}} data: {"type":"routing", "...": "..."} data: {"type":"delta","text":"Here is"} data: {"type":"done", "...": "..."} '400': description: Malformed request (`INVALID_BODY`). content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string '401': description: Not signed in (`UNAUTHENTICATED`). content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string '404': description: >- Organization or project not found (`ORG_NOT_FOUND`, `PROJECT_NOT_FOUND`). content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string '409': description: No models are configured for this project (`NO_MODELS`). content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string security: - session: [] components: securitySchemes: session: type: apiKey in: cookie name: session description: >- The session cookie set when you sign in to AgentHub or ModelHub in a browser. The cookie name shown here is illustrative. There are no API tokens for these endpoints. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.